This invention relates generally to the formation of electrical isolation regions in semiconductive structures and more particularly to thermally stable isolation regions in n-type indium phosphide substrates by oxygen implantation.
The necessity for selectively forming electrically isolated regions in certain types of semiconductive structures, such as monolithic integrated circuits is generally well-known. In the absence of providing some type of electrically insulating barrier between closely spaced semiconductive devices and/or other IC components fabricated in a common semiconductive substrate, undesirable leakage currents will flow between these devices or components and degrade the electrical performance of the structure, if not render it totally inoperable.
N-type InP is considered an excellent candidate for use in the formation of integrated circuits using electro-optics due to InP's good lattice matching capabilities with wave-guide materials such as InGaAs and InGaAsP and due to InP's high saturation velocity and good carrier mobility. A great need has developed to produce high-temperature stable isolation regions in n-type InP on Fe or Cr doped InP substrates for processes in which the isolation implantation precedes the alloying of ohmic contacts. A primary reason, though, why development of n-type InP on Fe or Cr doped InP substrates has not been carried further is the general acceptance that maximum benefits are achieved with implantation of light ions (H, He, Be and B) because the depth and benefits of the damage layer are inversely related to the ion mass and light ion bombardment has been shown to produce thermally stable isolation regions up to only 300.degree. C. Additionally, it has been shown that Hydrogen implantation into Cr doped InP produces a conductive layer. This results in a low-resistance shunt in parallel with the interdevice isolation.